This invention relates to the synthesis of a hydroxy-terminated linear carbonate by reacting a compound or polymer having one or more alcoholic hydroxyl groups with a cyclic alkylenecarbonate.
It is known that when a compound having one or more hydroxyl groups is reacted with a cyclic alkylenecarbonate, the hydroxyl group is converted into a hydroxy-terminated alkylcarbonate group by the addition of the cyclic alkylenecarbonate moiety to the hydroxyl group.
Japanese Laid Open Patent Application (Kokai) No. 56124/1980 discloses a process for producing a linear polycarbonate oligomer or polymer having a terminal hydroxyl groups by reacting a glycol with a cyclic alkylenecarbonate. A series of reactions takes place in this process. Firstly, the cyclic alkylenecarbonate is ring-opened with the glycol to produce a linear carbonate containing both of the hydrocarbon moieties corresponding to the glycol and cyclic carbonate reactants. Then, a transesterification occurs between the linear carbonate and the glycol with the formation of an alkylene glycol corresponding to the cyclic alkylenecarbonate as a by-product. The above reaction sequence continues to take place until the linear polycarbonate is chain-extended to a desired length. This process must be carried out under high vacuum to remove the alkylene glycol by-product from the reaction system. Therefore, the cyclic alkylenecarbonate used in the process is comparable, as a reactive derivative of carbonic acid, to phosgene conventionally used in the synthesis of polycarbonate polymers.